Generally, in an electronic control unit (ECU) front stage of a motor driven power steering (MDPS) system, a dark current (leakage current) is generated until vehicle ignition is turned on to discharge a vehicle battery.
FIG. 1 is a circuit diagram illustrating an ECU power circuit in the related art.
Referring to FIG. 1, when a Vlink voltage becomes 60% of a Vbat voltage through circuit path #10 during power up, the Vlink voltage is relayed on, and when the Vbat−Vlink voltage becomes a predetermined voltage or less after the relay on command, it can be confirmed that the relay on command is accurately applied.
During power down, in order to stably check a relay off after a relay off command, the Vlink voltage is reduced through a discharge circuit 13, and when the Vbat−Vlink voltage has a difference of a predetermined voltage or more, it can be confirmed that the relay off command is accurately applied.
As such, in the related art, even before the vehicle ignition is turned on, that is, even before an IGN_ENA signal is applied, a current path 11 is formed in the EC to generate the dark current (leakage current). Further, in order to prevent a large amount of dark current, since R426 and R427 resistances are largely set, during power down, the discharge circuit needs to be formed.